1. Field of the Invention
This invention pertains to moldable and melt-spinnable polyimide-esters and to tough high modulus filaments and films thereof.
2. Description of the Prior Art
A class of polyimide-esters that form optically anisotropic melts from which oriented filaments can be melt-spun has been described in Irwin U.S. Pat. No. 4,176,223. These polymers are derived from 2,6-naphthalene dicarboxylic acid and either (a) a substituted hydroquinone and 4-carboxy-N-(p-carboxyphenyl) phthalimide or (b) terephthalic acid and 4-hydroxy-N-(p-hydroxyphenyl)phthalimide. Filaments that are melt-spun from such polymers can be heat treated to develop high tenacity and modulus.
A melt processable aromatic polyester that forms an anisotropic melt and is derived from a para-oriented dihydric phenol, a para-oriented aromatic dicarboxylic acid and 6-hydroxy-2-naphthoic acid is disclosed in Calundann U.S. Pat. No. 4,256,624. Polyesters formed from combinations of para-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are disclosed in Calundann U.S. Pat. Nos. 4,161,470 and 4,219,461.
The present invention provides a new class of anisotropic-melt-forming polymers which can be melt cast into films or melt-spun into filaments which can be heat treated to provide products of high tenacity and modulus. The heat-treated products have unusual toughness compared to prior art products prepared from anisotropic melt polymers.